Recovery of Refrigerant from a Centrifugal Chiller
You are tasked with recovering refrigerant from a centrifugal chiller that uses R-123. The chiller has a charge of 350 kg. The system is being decommissioned. The chiller is located in a basement mechanical room with limited ventilation. The recovery machine you have is rated for R-123 but has a maximum recovery rate of 0.5 kg/min. The recovery cylinder available is a 50 kg capacity cylinder (tare weight 20 kg, total capacity 70 kg). The ambient temperature in the basement is 25°C. You need to recover the refrigerant safely and efficiently, and prepare for disposal. The chiller has a purge unit that contains some refrigerant as well.
1. What are the safety and regulatory considerations for recovering R-123 from this chiller, and how would you plan the recovery process?
Read the worked answer
R-123 is a low-pressure refrigerant with a boiling point of 27.8°C, so at 25°C it will be liquid under slight pressure. It is also an HCFC, but under F-gas? Actually R-123 is an HCFC, not covered by F-gas? F-gas regulation covers HFCs, PFCs, and SF6. R-123 is HCFC, so not under F-gas but under Montreal Protocol. However, the exam may still consider best practices. But for F-gas, R-123 is not an F-gas. However, the question might be about recovery best practices. Assuming it's for certification, recovery of any refrigerant should follow good practice. Safety: R-123 is toxic (A1? Actually ASHRAE safety group B1). It has low flammability? It is non-flammable but toxic. Need proper ventilation, personal protective equipment (respirator, gloves, goggles). Basement limited ventilation: use portable ventilation fans and monitor oxygen levels. Recovery: use a recovery machine designed for low-pressure refrigerants. Because of low pressure, you may need a liquid pump or use the chiller's pump to transfer liquid. Recovery rate 0.5 kg/min means 350 kg would take 700 minutes (about 11.7 hours). Plan for multiple days or use a larger machine. Cylinder capacity: 50 kg cylinder can hold max 80% of water capacity? For R-123, density is about 1.46 kg/L at 25°C. The cylinder volume? Typically, a 50 kg refrigerant cylinder has a water capacity of about 50 L? Actually, 50 kg cylinder might have a volume of about 50 L. 80% of 50 L = 40 L. At density 1.46 kg/L, max fill = 58.4 kg, but cylinder capacity is 50 kg, so the limiting factor is the cylinder's rated capacity? The cylinder is rated for 50 kg of refrigerant, so you can fill to 50 kg. So you need 7 cylinders (350/50 = 7). But you must not overfill; use a scale. Also, recover the purge unit refrigerant separately. Follow regulations: recover all refrigerant, not release to atmosphere. Use logbook and proper disposal.
2. How would you ensure complete recovery and handle the refrigerant for disposal?
Read the worked answer
To ensure complete recovery, use a recovery machine capable of pulling a vacuum on the chiller. For low-pressure refrigerants, you can use a liquid pump to remove the bulk liquid, then use the recovery machine to remove vapor. Monitor pressure to determine when recovery is complete; typically, evacuate to a vacuum of 500 microns? For R-123, you might need to reach a certain vacuum level. Use a vacuum gauge. Also, recover refrigerant from the purge unit and any oil. After recovery, the refrigerant in cylinders should be sent to a certified reclamation facility or destroyed. Do not mix with other refrigerants. Label cylinders properly. Keep records of the recovery amount and destination. Ensure cylinders are not overfilled and are secured during transport.